(a) Field of the Invention
The present invention relates to an electrophotographic element having a Se-Te-Cl system photoconductive layer.
(b) Description of the Prior Art
Since the selenium type electrophotographic element, whose photoconductive layer comprises selenium, utilized widely in the Xerox type electrophotography is hardly sensitive to the red color region, there is also utilized the element having the Te-doped Se layer in order to heighten the sensitivity to the red color region. However, the Se-Te system photoconductive layer of this type is defective in that the residual electric potential is heightened by the hole caused by exposure. In view of this, it has also been tried to neutralize the hole by additionally doping halogen on the Se-Te system photoconductive layer. However, the Se-Te-halogen system like this is defective in that as the amount of halogen added has opposite relationships with the temperature at the time of repetition use (thermal resistance), light fatigue characteristics and residual electric potential, the amount of halogen added must inevitably be restricted. For instance, in the case of Cl, unless it is added generally in excess of 30 ppm, the effect of restricting the residual electric potential is not achieved, and further, if it exceeds 30 ppm, the temperature necessary for repetition use (thermal resistance) and light fatigue characteristics deteriorate and consequently the charged electric potential decreases. It is known that said temperature and light fatigue characteristics are improved with effect by the addition of Sb, Ge and the like (which see Japanese Laid Open Patent Application No. 47654/1979, for instance, concerning the addition of Sb), but these components, as seen in the case of Sb, inversely bring about other drawbacks such as the increase in residual electric potential and the like and furthermore are difficult to be added in the thermal vacuum vapordeposition method, namely the generally known commercial layer forming method, because the vapor pressure of said components is low as compared with that of Se and Te.